Just before the weekend I read about a new technique which can be used to shoehorn around 1,000TB of data onto a “DVD disc”. This is quite a feat and it was achieved by circumnavigating some laws of physics with a technique which uses two different coloured light beams to selectively cancel each other out and produce a much finer beam – required for such a huge increase in data density.
Optical discs have their positive aspects, such as being cheap to produce as well as longevity and robustness but they are falling out of favour compared to other ways to back up or share data. Once thought of as an essential computer component, many people are now buying laptops that don’t include an optical disc reader or writer.
The storage capacity of a standard 12cm optical disc is limited by how small the pits burnt into its surface by a laser can be, itself limited by the diameter of the light beam doing the “burning” and the reading. The upgrade from DVD to Blu-ray was down to a finer laser beam and new media which could be “burnt” by that light beam.
In Physics, Abbe’s Law states that the width of light beams which can be“obtained by focussing the light through a lens, cannot be smaller than half its wavelength”. This means a visible light beam cannot be smaller than 500nm reports Phys.org. Using an optical two beam system comprised of a “writing beam” and an “inhibitor beam” it is possible to circumvent Abbe’s Law to create a practical laser beam that is less than 100nm in diameter, as shown in the diagram below. Phys.org says the scientists managed to achieve a laser of diameter significantly below 100nm; “This new technique produces an effective focal spot of nine nanometres – or one ten thousandth the diameter of a human hair”.
The diagram shows that the two beams are of different shapes and their overlaps cancel out to leave a much smaller focussed central light beam. Recording on the optical disc is “tightly confined to the centre” of this resulting light beam. Using this very fine laser to record on a 12cm optical disc should be able to yield capacities in the region of 1,000TB of data. This is equivalent to “10.6 years of compressed high-definition video or 50,000 full high-definition movies”.
The scientists say this new laser technique is “cost-effective and portable, as only conventional optical and laser elements are used, and allows for the development of optical data storage with long life and low energy consumption”. I’m looking forward to seeing this technology used in the first real-world devices which should be in “Big Data centres”according to the researchers. …
Archive for the ‘Physics’ Category
Posted by Xeno on June 24, 2013
Posted by Xeno on June 14, 2013
Warning: Turn your volume way down during this entire video. The sound that produces the patterns is loud enough to cause permanent hearing damage.
… This demonstration is by a prolific YouTube user who goes by the handle brusspup. I’ve been enjoying his amazing visual illusions for a few years – and I’m not the only one! His videos have wracked up tens of millions of views.
But this one isn’t an illusion. Rather, it’s a clever way to reveal patterns not normally visible to our senses. And it traces back to the 18th – and even the 17th – century and a somewhat obscure scientist.
Ernst Chladni was a German-born Hungarian physicist and musician who did pioneering work in acoustics and also in the study of meteorites.
In fact, in 1794, he was the first to publish the outlandish idea that meteorites were extraterrestrial in origin, a proposal for which he was ridiculed. At the time they were thought to be of volcanic origin. But we all know who got the last laugh on that one. He was vindicated within ten years – within his lifetime – when a dramatic meteor shower left hard-to-dispute meteoritic evidence all over a French town.
But the phenomenon seen in the video is the one for which Chladni is perhaps best known. It is a technique to reveal the complex patterns of vibration in a rigid surface.
A plate or membrane vibrating at resonance is divided into regions vibrating in opposite directions, bounded by lines of zero vibration called nodal lines… Chladni’s technique… consisted of drawing a bow over a piece of metal whose surface was lightly covered with sand. The plate was bowed until it reached resonance, when the vibration causes the sand to move and concentrate along the nodal lines where the surface is still, outlining the nodal lines.
Modern versions of the demonstration tend to use modern equipment such as loudspeakers and signal generators with adjustable frequency. In the video, as the frequency is altered we are able to see how the patterns in the plate assume various intricate shapes. The sand is pushed away from the areas of vibration and gathers in the places where the surface remains motionless (the nodal lines).
The beautiful patterns that emerge are now called Chladni figures, although Chladni was actually building on earlier experiments performed by Robert Hooke, who, in 1680, observed these nodal patterns in vibrating glass plates….
Is this effect seen in 2D here also a 3D phenomena? Since cells seem form, then break and reform new different cells, shuffling the cell contents non-biologically in the presence of vibration, this effect offers one way life may start to form. I’m visualizing vibration from an undersea volcano having this effect in 3D on surrounding suspended lipid and other molecules, forming hollow spheres (cells), jump starting life as we know it.
Posted by Xeno on June 6, 2013
The ultimate dream of nanotechnology is to be able to manipulate matter atom by atom. To do that, we first need to know what they look like. In what could be a major step in that direction, researchers have developed a method that can determine the shape of a single molecule and identify its constituent atoms.
The laws of nature limit what can be seen with the help of light alone. Only objects separated by less than half the wavelength of the light that illuminates it can be observed. To overcome this limit, in 1928, Edward Hutchinson Synge came up with an idea of imaging things too small for the naked eye. The idea was to shine light on a small particle and study the scattering when reflected back, making the wavelength of incident light irrelevant.
The realisation of Synge’s idea had to wait till the 1980s, when Heinrich Rohrer, the father of nanotechnology, developed scanning tunnelling microscopy (STM). This method uses a special property of electric current called quantum tunnelling to achieve this.
Since the development of STM, techniques for imaging smaller and smaller objects have been improving incrementally. Today it is possible to identify the shapes of molecules and where the atoms reside. But none of these techniques can identify the atoms those molecules are made of.
Now researchers from China, Spain and Sweden have combined STM with another method called Raman spectroscopy to determine not just the shape, but also the constituent atoms of a single molecule. …
When some form of energy, like heat or light, hits molecules it makes them vibrate and rotate, even in solid structures. This process is called “excitation”. The movement emits some of the energy back, which is called “emmission”. Raman spectroscopy works by detecting this tiny amount of emitted energy, which tells us things about the molecule that’s doing the emitting.
One of the many uses for Raman spectroscopy is analysing old ruined paintings. It can detect the presence of certain elements at very specific locations. The salts of these elements have specific colours and thus they can reveal what a particular part of the painting might have looked like originally.
Analyzing trillions of molecules is easy, because molecules of the same type will combine to produce a more intense signal, since they all experience the same vibrations and rotations. Where things become tricky is when single molecules need to be excited and their weak energy emission measured. Researchers led by Jianguo Hou, at the University of Science and Technology of China, have found a way to do that. The results of their work are published in the journal Nature today.
They use a modified STM technique that produces just enough light to excite only a few atoms of a molecule at a time. A laser is focused in a metal cavity which contains the molecule to be analysed. The laser’s energy creates an excited cloud of electrons called plamsons, which creates the local energy needed to excite different parts of a single molecule….
Posted by Xeno on May 31, 2013
When Felix Fischer of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) set out to develop nanostructures made of graphene using a new, controlled approach to chemical reactions, the first result was a surprise: spectacular images of individual carbon atoms and the bonds between them.
“We weren’t thinking about making beautiful images; the reactions themselves were the goal,” says Fischer, a staff scientist in Berkeley Lab’s Materials Sciences Division (MSD) and a professor of chemistry at the University of California, Berkeley. “But to really see what was happening at the single-atom level we had to use a uniquely sensitive atomic force microscope in Michael Crommie’s laboratory.” Crommie is an MSD scientist and a professor of physics at UC Berkeley.
What the microscope showed the researchers, says Fischer, “was amazing.” The specific outcomes of the reaction were themselves unexpected, but the visual evidence was even more so. “Nobody has ever taken direct, single-bond-resolved images of individual molecules, right before and immediately after a complex organic reaction,” Fischer says.
Posted by Xeno on May 28, 2013
It’s not the same as turning lead into gold, but scientists at the Illinois-based Argonne National Laboratory and the Japan Synchrotron Radiation Research Institute/SPring-8 have developed a method for turning cement into a liquid metal semiconductor.
The process sounds like a mad scientist’s invention. It involves equipment like an aerodynamic levitator and a carbon dioxide laser beam. The levitator uses gas pressure to keep the material out of contact with any container surfaces. The carbon dioxide laser beam can heat the material to 3,632 degrees Fahrenheit.
The material in question is mayenite, a calcium aluminum oxide material that is part of alimuna cement. It was placed in the aerodynamic levitator and thoroughly cooked until it melted. It was then allowed to cool down into a glassy state. This method resulted in a material that traps electrons and allows for conduction, effectively turning cement into a semiconductor that behaves much like metal does.
“This new material has lots of applications, including as thin-film resistors used in liquid-crystal displays, basically the flat panel computer monitor that you are probably reading this from at the moment,” Argonne physicist Chris Benmore said Monday in a statement.
The results is being published under the title “Network topology for the formation of solvated electrons in binary CaO-Al2O3 composition glasses” in the Proceedings of the National Academy of Sciences journal.
Score one for modern alchemy.
Posted by Xeno on May 24, 2013
The first direct observation of the orbital structure of an excited hydrogen atom has been made by an international team of researchers. The observation was made using a newly developed “quantum microscope”, which uses photoionization microscopy to visualize the structure directly. The team’s demonstration proves that “photoionization microscopy”, which was first proposed more than 30 years ago, can be experimentally realized and can serve as a tool to explore the subtleties of quantum mechanics….
The wavefunction is a central tenet of quantum theory – put simply, it contains the maximum knowledge that is available about the state of a quantum system. More specifically, the wavefunction is the solution to the Schrödinger equation. The square of the wavefunction describes the probability of where exactly a particle might be located at a given time. Although it features prominently in quantum theory, directly measuring or observing the wavefunction is no easy task, as any direct observation destroys the wavefunction before it can be fully observed.
In the past, “Rydberg wavepacket” experiments have tried to observe the wavefunction using ultrafast laser pulses. In these experiments, the atoms are in a superposition of their highly excited “Rydberg states”. These experiments show that the periodic electron orbitals around nuclei are described by coherent superpositions of quantum-mechanical stationary states. The wavefunction of each of these states is a standing wave with a nodal pattern (a “node” is where there is zero probability of finding an electron) that reflects the quantum numbers of the state. While previous experiments have attempted to capture the elusive wavefunction or the nodal patterns, the methods used were not successful. Direct observation of the nodal structure of a single atom being most difficult to achieve…
Posted by Xeno on May 19, 2013
Whether you need to brush up on your chemistry, or just love it when someone sets the Periodic Table to music, AsapSCIENCE’s The NEW Periodic Table Song is for you.
This rundown of the elements in numerical order is set to Jacques Offenbach’s Infernal Galop, but was otherwise written, produced, and performed by Mitchell Moffit. Here are the lyrics in case you missed anything:
There’s Hydrogen and Helium Then Lithium, Beryllium Boron, Carbon everywhere Nitrogen all through the air
With Oxygen so you can breathe And Fluorine for your pretty teeth Neon to light up the signs Sodium for salty times
Magnesium, Aluminium, Silicon Phosphorus, then Sulfur, Chlorine and Argon Potassium, and Calcium so you’ll grow strong Scandium, Titanium, Vanadium and Chromium and Manganese
CHORUS This is the Periodic Table Noble gas is stable Halogens and Alkali react agressively Each period will see new outer shells While electrons are added moving to the right
Iron is the 26th Then Cobalt, Nickel coins you get Copper, Zinc and Gallium Germanium and Arsenic
Selenium and Bromine film While Krypton helps light up your room Rubidium and Strontium then Yttrium, Zirconium
Niobium, Molybdenum, Technetium Ruthenium, Rhodium, Palladium Silver-ware then Cadmium and Indium Tin-cans, Antimony then Tellurium and Iodine and Xenon and then Caesium and…
Barium is 56 and this is where the table splits Where Lanthanides have just begun Lanthanum, Cerium and Praseodymium
Neodymium’s next too Promethium, then 62″s Samarium, Europium, Gadolinium and Terbium Dysprosium, Holmium, Erbium, Thulium Ytterbium, Lutetium
Hafnium, Tantalum, Tungsten then we’re on to Rhenium, Osmium and Iridium Platinum, Gold to make you rich till you grow old Mercury to tell you when it’s really cold
Thallium and Lead then Bismuth for your tummy Polonium, Astatine would not be yummy Radon, Francium will last a little time Radium then Actinides at 89
Actinium, Thorium, Protactinium Uranium, Neptunium, Plutonium Americium, Curium, Berkelium Californium, Einsteinium, Fermium Mendelevium, Nobelium, Lawrencium Rutherfordium, Dubnium, Seaborgium Bohrium, Hassium then Meitnerium Darmstadtium, Roentgenium, Copernicium
Ununtrium, Flerovium Ununpentium, Livermorium Ununseptium, Ununoctium And then we’re done!!
This one is my favorite, it doesn’t hit them all, but it rocks out and has great additional information.
Posted by Xeno on May 17, 2013
Graphene has dazzled scientists, ever since its discovery more than a decade ago, with its unequalled electronic properties, its strength and its light weight. But one long-sought goal has proved elusive: how to engineer into graphene a property called a band gap, which would be necessary to use the material to make transistors and other electronic devices.
Now, new findings by researchers at MIT are a major step toward making graphene with this coveted property. The work could also lead to revisions in some theoretical predictions in graphene physics.
The new technique involves placing a sheet of graphene — a carbon-based material whose structure is just one atom thick — on top of hexagonal boron nitride, another one-atom-thick material with similar properties. The resulting material shares graphene’s amazing ability to conduct electrons, while adding the band gap necessary to form transistors and other semiconductor devices.
The work is described in a paper in the journal Science co-authored by Pablo Jarillo-Herrero, the Mitsui Career Development Assistant Professor of Physics at MIT, Professor of Physics Ray Ashoori, and 10 others.
“By combining two materials,” Jarillo-Herrero says, “we created a hybrid material that has different properties than either of the two.”
Graphene is an extremely good conductor of electrons, while boron nitride is a good insulator, blocking the passage of electrons. “We made a high-quality semiconductor by putting them together,” Jarillo-Herrero explains. Semiconductors, which can switch between conducting and insulating states, are the basis for all modern electronics.
To make the hybrid material work, the researchers had to align, with near perfection, the atomic lattices of the two materials, which both consist of a series of hexagons. The size of the hexagons (known as the lattice constant) in the two materials is almost the same, but not quite: Those in boron nitride are 1.8 percent larger. So while it is possible to line the hexagons up almost perfectly in one place, over a larger area the pattern goes in and out of register.
At this point, the researchers say they must rely on chance to get the angular alignment for the desired electronic properties in the resulting stack. However, the alignment turns out to be correct about one time out of 15, they say.
“The qualities of the boron nitride bleed over into the graphene,” Ashoori says. But what’s most “spectacular,” he adds, is that the properties of the resulting semiconductor can be “tuned” by just slightly rotating one sheet relative to the other, allowing for a spectrum of materials with varied electronic characteristics.
Others have made graphene into a semiconductor by etching the sheets into narrow ribbons, Ashoori says, but such an approach substantially degrades graphene’s electrical properties. By contrast, the new method appears to produce no such degradation.
Researchers from the University of Manchester discovered that sandwiching graphene between boron nitride layers can produce highly-accurate capacitors. Such capacitors could be cheaper and easier to fabricate compared to traditional transistors.
The researchers used quantum capacitance spectroscopy to investigate the exceptional properties of graphene …
Posted by Xeno on May 17, 2013
Yet in fact, these are microscopic crystals grown in a Harvard laboratory.
Measuring just microns across, they were created to assemble themselves a molecule at a time.
The team say the work, carried out on glass slides, is able to control the process of crystal growth so precisely it can create curved and delicate shapes, that don’t resemble the cubic or jagged forms normally associated with crystals.
“Rather, fields of carnations and marigolds seem to bloom from the surface of a submerged glass slide, assembling themselves a molecule at a time,” the team say.
“For at least 200 years, people have been intrigued by how complex shapes could have evolved in nature.
“This work helps to demonstrate what’s possible just through environmental, chemical changes,” said Wim L. Noorduin of the Harvard School of Engineering and Applied Sciences (SEAS) and lead author of the paper in the journal Science.
By simply manipulating chemical gradients in a beaker of flui the team was able to create different “flowers”.
The shape of the crystals depends on a reaction of compounds that are diffusing through a liquid solution.
The crystals grow toward or away from certain chemical gradients as the pH of the reaction shifts back and forth.
The conditions of the reaction dictate whether the structure resembles broad, radiating leaves, a thin stem, or a rosette of petals, the team say.
“It is not unusual for chemical gradients to influence growth in nature; for example, delicately curved marine shells form from calcium carbonate under water, and gradients of signaling molecules in a human embryo help set up the plan for the body,” they say.
“You can really collaborate with the self-assembly process,” says Noorduin.
“The precipitation happens spontaneously, but if you want to change something then you can just manipulate the conditions of the reaction and sculpt the forms while they’re growing.”
Increasing the concentration of carbon dioxide, for instance, helps to create “broad-leafed” structures.
Reversing the pH gradient at the right moment can create curved, ruffled structures.
Noorduin and his colleagues have grown the crystals on glass slides and metal blades; they’ve even grown a field of flowers in front of President Lincoln’s seat on a one-cent coin. …
Harvard biologist Howard Berg has shown that bacteria living in colonies can sense and react to plumes of chemicals from one another, which causes them to grow, as a colony, into intricate geometric patterns.
Replicating this type of effect in the laboratory was a matter of identifying a suitable chemical reaction and testing, again and again, how variables like the pH, temperature, and exposure to air might affect the nanoscale structures….
Some see the complexity and beauty of nature and conclude an intelligent designer. Others note that environmental variation and small local chemical interactions which follow the laws of physics result in self-organizing systems forming patterns we recognize as life. The duties of our deities are reduced, year by year.
Posted by Xeno on May 17, 2013
A normal digital camera can take snaps of objects not directly visible to its lens, US researchers have shown. The “ghost imaging” technique could help satellites take snapshots through clouds or smoke.
Physicists have known for more than a decade that ghost imaging is possible. But, until now, experiments had only imaged the holes in stencil-like masks, which limited its potential applications.
Now Yanhua Shih of the University of Maryland, Baltimore, and colleagues at the US Army Research Laboratory, also in Maryland, have now taken the first ghost images of an opaque object – a toy soldier …
Ghost imaging works a bit like taking a flash-lit photo of an object using a normal camera. There the image forms from photons that come out of the flash, bounce off an object and into the lens.
The new technique also uses a light source to illuminate an object. However, the image is not formed from light that hits the object and bounces back. Instead, the camera collects photons that do not hit the object, but are paired through a quantum effect with others that did.
In Shih’s experiments a toy soldier was placed 45 centimetres away from a light source, which was split into two beams. One was pointed at the toy and the other at a digital camera. A photon detector was placed near the soldier, able only to record when a photon bounced off.
Photons from the light source constantly travel down both paths made by the splitter, either towards the soldier and the photon detector, or towards the camera. The detector and camera record a constant stream of those photons, and occasionally record a photon at exactly the same time.
When this happens, there is a direct relationship between where one of the photons hit the soldier, and where the other one hits the camera’s sensor, says Shih, because of a quantum effect called “two-photon interference”.
“If the first photon stops at one point on the object plane, the second photon can only be observed at the corresponding point on the image plane,” he says.
So when the camera records only pixels from photons that hit simultaneously with one reaching the detector, a “ghost image” of the object builds up. The soldier’s image appeared after around 1000 coincidental photons were recorded.
“It is clear that the experimental set-up can be directly applied to sensing applications,” Shih told New Scientist .
The same method could one day be employed to produce satellite images of objects hidden behind clouds or smoke, using the sun’s radiation as the photon source, says Shih. Doing that may require a photon counter beneath the clouds, but could allow a top-down view not possible using conventional methods.
Not everyone agrees that quantum effects are at work in ghost imaging, though. Baris Erkmen and Jeffrey Shapiro of the Massachusetts Institute of Technology, Cambridge, US, point out in a recent paper that classical physics says light sources produce numbers of uncoordinated photons that are not correlated as Shih suggests.
They suspect ghost images might be produced without a quantum link between photon pairs, purely because some photons are just similar. …